Fuel cells can generally be classified into alkaline, solid oxide, and proton exchange membrane fuel cells. The proton exchange membrane fuel cell has received increasingly more attention and has developed rapidly in recent years. Typically, the proton exchange membrane fuel cell includes a number of separated fuel cell work units. Each work unit includes a fuel cell membrane electrode assembly (MEA), flow field plates (FFP), current collector plates (CCP), as well as related support equipments, such as blowers, valves, and pipelines.
Referring to FIG. 12, the MEA 50 generally includes a proton exchange membrane 51 and two electrodes 54 located adjacent to two opposite surfaces of the proton exchange membrane 51 according to the prior art. Furthermore, each electrode 54 includes a catalyst layer 52 and a diffusion layer 53. The catalyst layer 52 is sandwiched between the diffusion layer 53 and the proton exchange membrane 51. The proton exchange membrane 51 is typically made of a material selected from the group consisting of erfluorosulfonic acid, polystyrene sulfonic acid, polystyrene trifluoroacetic acid, phenol formaldehyde resin acid, and hydrocarbons. The catalyst layer 52 includes catalyst materials and carriers. The catalyst materials can be metal particles, such as platinum particles, gold particles, ruthenium particles or combinations thereof. The carriers are generally carbon particles, such as graphite, carbon black, carbon fiber or carbon nanotubes. The diffusion layer 53 is constituted of carbon fiber paper.
However, the carbon fiber paper has the following disadvantages. Firstly, the carbon fibers in the carbon fiber paper are not uniformly dispersed, and therefore, the micropores therein defined by the carbon fibers are not uniform. Thus, such structure prevents the diffusion layer from uniformly diffusing the gases that are needed for the MEA. Secondly, the carbon fiber paper has high electrical resistance, thereby the travel of electrons between the diffusion layer and the external electrical circuit is restricted. As a result, the reaction activity of the MEA is reduced.
What is needed, therefore, are a membrane electrode assembly and a fuel cell using the same having improved reaction activity.